The Silenced (2015)

Back in 1938, when Korea was under Japanese colonial rule, Joo-Ran is transferred to an all-girl's boarding school in Keijyo (old name of Seoul). The principal there exhibits exemplary behavior to all of the students, but she ends up showing her darker side to Joo-Ran, who gets close to knowing the school's biggest secret. The girl learns of another student with the same name and she tries to figure out the hidden stories that happened at the girl students' dormitory.